Radio Frequency Signal Control Module and Radio Frequency Signal Controlling Method

ABSTRACT

A radio frequency (RF) signal control module is provided. The RF signal control module includes a detection and control device detecting at least one radio coupling value in a transmission band according to a radio coupling signal and generating a control signal for controlling transmission power an RF signal to be transmitted according to the detected radio coupling value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/384,523 filed Sep. 20, 2010 and entitled “OMNI-DIRECTIONAL SARCALIBRATION”. The entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a radio frequency (RF) signal control module,and more particularly to an RF signal control module that is capable ofomni-directional detection of radio coupling values and accordinglycontrolling the transmission power of a communications device.

2. Description of the Related Art

Specific absorption rate (SAR) is a measure of the rate at which radiofrequency (RF) energy is absorbed by a human body when exposed to aradio-frequency electromagnetic field. It is defined as the powerabsorbed per mass of tissue and has units of Watts per kilogram. SAR isusually averaged either over the whole body, or over a small samplevolume (typically 1 g or 10 g of tissue). The value cited is then themaximum level measured in the body part studied over the stated volumeor mass. It may be calculated from the electric field within the tissueas:

${{SAR} = \frac{\sigma {E}^{2}}{2\rho}},$

where σ represents the sample electrical conductivity, |E| representsthe magnitude of the electric field and ρ represents the sample density.

Conventionally, a proximity sensor is embedded in an electronic devicefor SAR calibration. Once the proximity sensor has detected that a humanbody is close to the electronic device, a maximum RF transmission poweris limited. However, the proximity sensor is a directional device. Themore directions that are required to be detected for calibration, themore proximity sensors required to be provided.

Therefore, a novel design for transmission power detection and controlwithout directional limitations is highly required.

BRIEF SUMMARY OF THE INVENTION

A radio frequency (RF) signal control module and RF signal controllingmethod are provided. An embodiment of an RF signal control modulecomprises a detection and control device. The detection and controldevice detects at least one radio coupling value in a transmission bandaccording to a radio coupling signal and generates a control signal forcontrolling transmission power of an RF signal to be transmittedaccording to the detected radio coupling value.

An embodiment of an RF signal controlling method comprises: detecting anamount of change of a radio coupling value according to a radio couplingsignal; determining whether the amount of radio coupling value changehas exceeded a predetermined threshold; and limiting a maximumtransmission power of an RF signal to be transmitted or lowering atransmission power of an RF signal to be transmitted by a levelaccording to the detected radio coupling value when the amount of radiocoupling value change has exceeded the predetermined threshold.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 shows a schematic block diagram of a communications apparatusaccording to an embodiment of the invention;

FIG. 2 shows a schematic block diagram of the RF signal control moduleaccording to an embodiment of the invention;

FIG. 3 shows a schematic block diagram of a communications apparatusaccording to an embodiment of the invention;

FIG. 4 shows a schematic block diagram of a communications apparatusaccording to another embodiment of the invention;

FIG. 5 shows a schematic diagram of a coupler 528 according to anembodiment of the invention;

FIG. 6 shows a schematic block diagram of the detection and controldevice according to an embodiment of the invention;

FIG. 7 shows a schematic block diagram of a communications apparatusequipped with multiple transmission antennas according to anotherembodiment of the invention;

FIG. 8 shows a schematic block diagram of a communications apparatusequipped with multiple transmission antennas according to anotherembodiment of the invention; and

FIG. 9 shows a flow chart of an RF signal controlling method accordingto an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 1 shows a schematic block diagram of a communications apparatusaccording to an embodiment of the invention. The communicationsapparatus 100 may at least comprise a transceiver module 102 and a radiofrequency (RF) signal control module 104. The transceiver module 102 isarranged to generate an RF signal S_(RF) to be transmitted to the airinterface. The RF signal control module 104 is arranged to generate acontrol signal S_(Ctrl) to adjust transmission power utilized by thetransceiver module 102 for transmitting the RF signal S_(RF). It shouldbe noted that for clear illustration of the invention concept, only thedevices related to the proposed design are illustrated in FIG. 1, andtherefore, the invention should not be limited thereto.

According to an embodiment of the invention, the RF signal controlmodule 104 obtains or receives a radio coupling signal S_(Couple) andgenerates the control signal S_(Ctrl) according to the radio couplingsignal S_(Couple). In the embodiments of the invention, the radiocoupling signal S_(Couple) is corresponding to transmission of the RFsignal S_(RF).

FIG. 2 shows a schematic block diagram of the RF signal control moduleaccording to an embodiment of the invention. The RF signal controlmodule 104 may comprise a radio coupling device 202 and a detection andcontrol device 204. The radio coupling device 202 is arranged to obtainor receive the radio coupling signal S_(Couple) in a transmission bandthrough a radio coupling path established between a transmission antennatransmitting the RF signal S_(RF) and the RF signal control module 104(which will be discussed in more detail in the following paragraphs).The detection and control device 204 is arranged to detect at least oneradio coupling value according to the radio coupling signal S_(Couple),and generates the control signal S_(Ctrl) for controlling transmissionpower of the RF signal S_(RF) to be transmitted later according to thedetected radio coupling value.

According to an embodiment of the invention, the radio coupling device202 may be implemented by a sensor antenna for receiving the radiocoupling signal S_(Couple). In the embodiment, the radio coupling signalS_(Couple) may be a faded version of the RF signal S_(RF). FIG. 3 showsa schematic block diagram of a communications apparatus 300 according toan embodiment of the invention. As shown in FIG. 3, the transceivermodule 302 is coupled to a transmission antenna 324 for transmitting theRF signal S_(RF) generated thereby. Note that in some embodiments, thetransmission antenna 324 may also be integrated in the transceivermodule 302 and the invention should not be limited thereto. The RFsignal control module 104 may comprise the detection and control device304 and a sensor antenna 326. The transmitted RF signal S_(RF) may bereceived by the sensor antenna 326 from the radio coupling path 330between the transmission antenna 324 and the sensor antenna 326. Becausethe radio coupling is omni-directional and fixed from the transmissionantenna 324 to the sensor antenna 326, according to an embodiment of theinvention, the detection and control device 304 may detect and monitorthe power or phase of the radio coupling signal S_(Couple), or any otherradio coupling value according to the radio coupling signal S_(Couple),and determine whether a currently detected radio coupling value hasexceeded a predetermined threshold determined when there is no humanbody close to the communications apparatus 300. When the radio couplingvalue is determined to have exceeded the predetermined threshold, thedetection and control device 304 may determine that there is at leastone human body close to the communications apparatus 300, and generatethe control signal S_(Ctrl) for limiting the maximum transmission powerof the transceiver module 302 or lowering the transmission power of theRF signal S_(RF) to be transmitted later by a certain level. Therefore,the possible RF energy absorbed by the human body when exposed to radiofrequency electromagnetic field is reduced. Note that in someembodiments of the invention, the predetermined threshold may also beset as an amount of possible change of the radio coupling valuedetermined when there is no human body close to the communicationsapparatus 300. The detection and control device 304 may detect andmonitor the amount of change of the radio coupling value. When theamount of radio coupling value change has exceeded the predeterminedthreshold, the detection and control device 304 may determine that thereis at least one human body close to the communications apparatus 300,and generate the control signal S_(Ctrl) for limiting the maximumtransmission power of the transceiver module 302 or lowering thetransmission power of the RF signal S_(RF) to be transmitted later by acertain level. Note also that in other embodiments, the predeterminedthreshold may also be set as a percentage or an absolute value ofpredetermined radio coupling value or an amount of possible change ofthe radio coupling value determined when there is no human body close tothe communications apparatus, or may be set as other values based on thesimilar concepts, and the invention should not be limited to theexamples as described above.

According to an embodiment of the invention, an ideal radio couplingvalue or the ideal amount of possible change of the radio coupling valuewhen there is no human body close to the communications apparatus isfirst determined. For example, suppose that when there is no human bodyclose to the communications apparatus 300, the power of the transmittedRF signal S_(RF) is 23 dBm and the power of the received radio couplingsignal S_(Couple) is −7 dBm, and therefore, the ideal radio couplingpath loss is obtained by (−7−23)=30 dBm. A 10% margin may be applied, sothat the predetermined threshold of the radio coupling path loss may bedetermined as 33 dBm. In other words, once a currently obtained radiocoupling path loss determined by the detection and control device 304has exceeded 33 dBm, the detection and control device 304 may determinethat there is at least one human body close to the communicationsapparatus 300, and generate the control signal S_(Ctrl) for limiting themaximum transmission power of the transceiver module 302.

For another example, an ideal phase of the received radio couplingsignal S_(Couple) may first be measured when there is no human bodyclose to the communications apparatus 300. The phase component may beobtained from the imaginary part of the received radio coupling signalS_(Couple). A suitable margin may also be applied, so as to determineone or more predetermined thresholds corresponding to the phase of thereceived radio coupling signal S_(Couple). Once a currently obtainedphase of the received radio coupling signal S_(Couple) is determined tobe different from the predetermined threshold(s), the detection andcontrol device 304 may determine that there is at least one human bodyclose to the communications apparatus 300, and generate the controlsignal S_(Ctrl) for limiting the maximum transmission power of thetransceiver module 302 or lowering the transmission power of the RFsignal S_(RF) to be transmitted later by a certain level.

According to another embodiment of the invention, the radio couplingdevice 202 may be implemented by a coupler for obtaining the radiocoupling signal S_(Couple). In the embodiment, the radio coupling signalS_(Couple) may be a reflected (or returned) version of the RF signalS_(RF). FIG. 4 shows a schematic block diagram of a communicationsapparatus 400 according to another embodiment of the invention. As shownin FIG. 4, a coupler 428 is coupled between a transmission antenna 424for transmitting the RF signal S_(RF) and a power amplifier 422. Thepower amplifier 422 is comprised in the transceiver module 402. Notethat in some embodiments, the transmission antenna 424 may also beintegrated in the transceiver module 402 and the invention should not belimited thereto. Note also that in some embodiments, the coupler may beintegrated in the power amplifier 422, or embedded on the printedcircuit board, and the invention should not be limited thereto. FIG. 5shows a schematic diagram of a coupler 528 according to an embodiment ofthe invention. The coupler 528 may comprise an input port 501 forreceiving the RF signal S_(RF) from the power amplifier 422, atransmitted port 502 for outputting the RF signal S_(RF) and receivingthe reflected (or returned) RF signal S′_(RF), a coupled port 503 forcoupling the reflected (or returned) RF signal S′_(RF) to generate theradio coupling signal S_(Couple) and an isolated port 504. Referringback to FIG. 4, according to an embodiment of the invention, thedetection and control device 404 may detect and monitor the power orphase of the radio coupling signal S_(Couple), or any other radiocoupling value (such as an impedance of the transmission antenna 424)according to the radio coupling signal S_(Couple), and determine whetherthe radio coupling value or the amount of radio coupling value changehas exceeded a predetermined threshold determined when there is no humanbody close to the communications apparatus 400. When the radio couplingvalue or the amount of radio coupling value change is determined to haveexceeded the predetermined threshold, the detection and control device404 may determine that there is at least one human body close to thecommunications apparatus 400, and generate the control signal S_(Ctrl)for limiting the maximum transmission power of the transceiver module402 or lowering the transmission power of the RF signal S_(RF) to betransmitted later by a certain level. Therefore, the possible RF energyabsorbed by the human body when exposed to radio frequencyelectromagnetic field is reduced.

For example, an ideal impedance of the transmission antenna 424 mayfirst be measured when there is no human body close to thecommunications apparatus 400. The impedance of the transmission antenna424 may be obtained by measuring an S parameter corresponding to thetransmission antenna 424. For example, when the coupler 428 is amulti-port device with port 1 P1 and port 2 P2, the measured inputreturn loss S₁₁ may be representable of the impedance of thetransmission antenna 424. To be more specific, the detection and controldevice 404 may obtain an ideal input return loss S₁₁ according to aratio of the radio coupling signal S_(Couple) to the RF signal S_(RF)when there is no human body close to the communications apparatus 400.Suppose that the obtained ideal input return loss S₁₁ is expressed byS₁₁=a+bj, where the a and b are real numbers, and j is a mathematicalsymbol which is called the imaginary unit. The detection and controldevice 404 may take the imaginary part number b as the radio couplingvalue to represent the impedance of the transmission antenna 424.Similarly, a suitable margin may also be applied, so as to determine thepredetermined threshold corresponding to the impedance of thetransmission antenna 424. Once a currently obtained input return lossS_(ii) (or currently obtained impedance of the transmission antenna 424)is determined to have exceeded the predetermined threshold, thedetection and control device 404 may determine that there is at leastone human body close to the communications apparatus 400, and generatethe control signal S_(Ctrl) for limiting the maximum transmission powerof the transceiver module 402 or lowering the transmission power of theRF signal S_(RF) to be transmitted later by a certain level.

Note that in other embodiments of the invention, the other informationobtained from the measured input return loss S₁₁ may also be taken asthe radio coupling value. For example, the real part number a, or acombination of the real part and imaginary part numbers a and b, such as√{square root over (a²+b²)}, may also be taken as the radio couplingvalue. Besides the input return loss S₁₁, the insertion loss S₂₁ mayalso be obtained as the radio coupling value and the invention shouldnot be limited thereto. For example, when the insertion loss S₂₁ isexpressed by S₂₁=c+dj, where the c and d are real numbers, the real partnumber c, the imaginary part number d, or a combination of the real partand imaginary part numbers c and d, such as √{square root over (c²+d²)},may also be taken as the radio coupling value.

FIG. 6 shows a schematic block diagram of the detection and controldevice according to an embodiment of the invention. The detection andcontrol device 604 may comprise a detector 641, a sampler 642, acomparator 643 and a memory 644. According to an embodiment of theinvention, the detector 641 may receive the radio coupling signalS_(Couple) from the radio coupling device, and detect the radio couplingvalue and/or the amount of radio coupling value change according to theradio coupling signal S_(Couple). For example, the detector 641 maydetect the power and/or power change of the radio coupling signalS_(Couple) by performing waveform to voltage conversion. For anotherexample, the detector 641 may detect the phase and/or phase change ofthe radio coupling signal S_(Couple) by extracting the imaginary part ofthe radio coupling signal S_(Couple). For yet another example, thedetector 641 may detect the impedance and/or impedance change of thetransmission antenna by measuring the S parameter in the transceivernetwork. The value S_(V) detected by the detector 641 may further besampled by the sampler 642. The sampler 642 may be, for example, ananalog to digital converter. The sampled value S_(V)′ may be furtherpassed to the comparator 643. The comparator 643 may compare the sampledvalue S_(V)′ with a predetermined threshold value TH stored in thememory 644, and generate the control signal S_(Ctrl) according to thecomparison result. Note that FIG. 6 only shows one exemplary design ofthe detection and control device, and the invention should not belimited thereto. In addition, in the embodiments of the invention, thedetection and control device may be implemented by dedicated hardware,or the functions performed by the detection and control device asdescribed above may be coded as some software instructions executed by ageneral purpose processor. Therefore, the invention should not belimited to either cases.

FIG. 7 shows a schematic block diagram of a communications apparatusequipped with multiple transmission antennas according to anotherembodiment of the invention. The communications apparatus 700 may atleast comprise two transmission antennas 724 and 726 for simultaneouslytransmitting the RF signal (the MIMO case) or not simultaneouslytransmitting the RF signal (the antenna selection case). In theembodiment, two radio coupling devices 706 and 708 are utilized anddisposed close to the transmission antennas 724 and 726 for detectingthe radio coupling signals, respectively. For example, for the MIMOcase, both of the transmission antennas 724 and 726 are utilized fortransmitting the RF signals. The radio coupling devices 706 and 708disposed close to the transmission antennas 724 and 726 may respectivelydetect the radio coupling signals reflected to the transmission antennas724 and the transmission antennas 726, or detect the radio couplingsignal coupled from the transmission antennas 726 (or 724) to thetransmission antennas 724 (or 726). For another example, for the antennaselection case, when the transmission antennas 724 is utilized fortransmitting the RF signal and the transmission antennas 726 is notutilized for transmitting the RF signal, the radio coupling device 708corresponding to the transmission antennas 726 may be utilized to detectthe radio coupling signal coupled from the transmission antennas 724 tothe transmission antennas 726, and vise versa. The received couplingsignals are further transmitted to the detection and control device 704for transmission power control. It should be noted that FIG. 7 is asimplified block diagram with a lot of devices configured inside of thecommutations device omitted for clear illustration of the inventionconcept. Therefore, the invention should not be limited thereto. Itshould also be noted that when there are more than one transmissionantenna utilized for transmitting the RF signals (for example, the MIMOcase), the radio coupling value(s) may be obtained according to oneradio coupling signal corresponding to either one transmission antenna,or according to the radio coupling signals obtained corresponding to themultiple transmission antennas, or according to a combination result ofthe radio coupling signals corresponding to multiple transmissionantennas, or others. The way to determine the predetermined thresholdmay also be varied based on the mechanism of obtaining the radiocoupling value.

FIG. 8 shows a schematic block diagram of a communications apparatusequipped with multiple transmission antennas according to anotherembodiment of the invention. The communications apparatus 800 may atleast comprise two transmission antennas 824 and 826 for simultaneouslytransmitting the RF signal (the MIMO case) or not simultaneouslytransmitting the RF signal (the antenna selection case). In theembodiment, one radio coupling device 806 is utilized and disposed closeto (or between) the transmission antennas 824 and 826 for detecting theradio coupling signal. For example, for the MIMO case, both of thetransmission antennas 824 and 826 are utilized for transmitting the RFsignals. The radio coupling device 806 may detect the radio couplingsignals reflected to the transmission antennas 824 and the transmissionantennas 826, or detect the radio coupling signal coupled from thetransmission antennas 826 (or 824) to the transmission antennas 824 (or826). For another example, for the antenna selection case, when thetransmission antennas 824 is utilized for transmitting the RF signal andthe transmission antennas 826 is not utilized for transmitting the RFsignal, the radio coupling device 806 may be utilized to detect theradio coupling signal coupled from the transmission antennas 824 to thetransmission antennas 826, and vise versa. The received coupling signalsare further transmitted to the detection and control device 804 fortransmission power control. It should be noted that FIG. 8 is asimplified block diagram with a lot of devices configured inside of thecommutations device omitted for clear illustration of the inventionconcept. Therefore, the invention should not be limited thereto. Itshould also be noted that in some embodiments of the invention, for theantenna selection case as previously described, the transmission antennathat is not utilized for transmitting the RF signal may also function asthe radio coupling device for receiving or obtaining the radio couplingsignal S_(Couple). In this case, a dedicated radio coupling device (suchas the radio coupling device 706, 708 or 806 as shown in FIG. 7 and FIG.8) can be omitted.

FIG. 9 shows a flow chart of an RF signal controlling method accordingto an embodiment of the invention. To begin, an amount of change of aradio coupling value corresponding to a communications apparatus may bedetected according to a radio coupling signal (Step S902). Next, it isdetermined whether the amount of radio coupling value change hasexceeded a predetermined threshold (Step S904). When the amount of radiocoupling value change has not exceeded a predetermined threshold, it isdetermined that there is no human body close to the correspondingcommunications apparatus and the process may be ended. Otherwise, amaximum transmission power of the communications apparatus fortransmitting an RF signal may be limited or a transmission power of theRF signal S_(RF) to be transmitted later may be lowered by a certainlevel according to the amount of radio coupling value change (StepS906). Note that when it is determined that there is any human bodyclose to the corresponding communications apparatus, the maximumtransmission power is limited to a smaller possible value as defined bythe corresponding specifications so as to reduce possible RF energyabsorbed by the human body. In other embodiments, the transmission powerof the communications apparatus for transmitting an RF signal may alsobe directly reduced according to the detected radio coupling value, andthe invention should not be limited thereto. The flow as shown in FIG. 9may be repeated periodically, so as to dynamically control thetransmission power of the communications apparatus.

The above-described embodiments of the present invention can beimplemented in any of numerous ways. For example, the embodiments may beimplemented using hardware, software or a combination thereof. It shouldbe appreciated that any component or collection of components thatperform the functions described above can be generically considered asone or more processors that control the above discussed function. Theone or more processors can be implemented in numerous ways, such as withdedicated hardware, or with general purpose hardware that is programmedusing microcodes or software to perform the functions recited above.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. Those who are skilled in this technology can still makevarious alterations and modifications without departing from the scopeand spirit of this invention. Therefore, the scope of the presentinvention shall be defined and protected by the following claims andtheir equivalents.

What is claimed is:
 1. A radio frequency (RF) signal control module,comprising: a detection and control device, detecting at least one radiocoupling value in a transmission band according to a radio couplingsignal and generating a control signal for controlling transmissionpower of an RF signal to be transmitted according to the detected radiocoupling value.
 2. The RF signal control module as claimed in claim 1,further comprising: a radio coupling device, obtaining the radiocoupling signal from a radio coupling path between a transmissionantenna utilized for transmitting the RF signal and the radio couplingdevice.
 3. The RF signal control module as claimed in claim 2, whereinthe radio coupling device is an antenna.
 4. The RF signal control moduleas claimed in claim 2, wherein the radio coupling device is a coupler.5. The RF signal control module as claimed in claim 1, wherein the radiocoupling value is power of the radio coupling signal.
 6. The RF signalcontrol module as claimed in claim 1, wherein the radio coupling valueis a phase of the radio coupling signal.
 7. The RF signal control moduleas claimed in claim 1, wherein the radio coupling value is an impedanceof a transmission antenna utilized for transmitting the RF signal. 8.The RF signal control module as claimed in claim 1, wherein the radiocoupling signal is a faded version of the RF signal.
 9. The RF signalcontrol module as claimed in claim 1, wherein the radio coupling signalis a reflected version of the RF signal.
 10. The RF signal controlmodule as claimed in claim 1, wherein the radio coupling value isdetected by measuring an S parameter corresponding to a transmissionantenna utilized for transmitting the RF signal.
 11. The RF signalcontrol module as claimed in claim 1, wherein the detection and controldevice further comprises: a memory, storing a predetermined thresholdvalue; a detector, detecting the radio coupling value according to theradio coupling signal; a sampler, sampling the detected radio couplingvalue to obtain a sampled radio coupling value; and a comparator,comparing the sampled radio coupling value with the predeterminedthreshold value and generating the control signal according to acomparison result.
 12. A radio frequency (RF) signal controlling method,comprising: detecting an amount of change of a radio coupling valueaccording to a radio coupling signal; determining whether the amount ofradio coupling value change has exceeded a predetermined threshold; andlimiting a maximum transmission power of an RF signal to be transmittedor lowering a transmission power of an RF signal to be transmitted by alevel when the amount of radio coupling value change has exceeded thepredetermined threshold.
 13. The method as claimed in claim 12, furthercomprising: obtaining the radio coupling signal from a radio couplingpath coupled to a transmission antenna utilized for transmitting an RFsignal.
 14. The method as claimed in claim 12, wherein the radiocoupling signal is a faded version of the RF signal.
 15. The method asclaimed in claim 12, wherein the radio coupling signal is a reflectedversion of the RF signal.
 16. The method as claimed in claim 12, whereinthe radio coupling value is power of the radio coupling signal.
 17. Themethod as claimed in claim 12, wherein the radio coupling value is aphase of the radio coupling signal.
 18. The method as claimed in claim12, wherein the radio coupling value is an impedance of a transmissionantenna utilized for transmitting the RF signal.
 19. The method asclaimed in claim 12, wherein the detecting step further comprising:measuring an S parameter corresponding to a transmission antennautilized for transmitting an RF signal.